Sitting at my daughters dance recital, and since it’s a long (long) time till she dances and I’m a male and bored, I was thinking more on the fair use defense. So I slipped out into the lobby to share my sudden insight and brilliance.
First, I want to say if you use other peoples copyrighted works and claim, at the time you used it that is was done as fair use, please stop. Fair use is a defense against a claim of copyright infringement. Until they claim is made, there is only use. Why admit you knowingly infringed before someone files a claim.
Anyone who tells you they are absolutely, 100% certain they will win a fair use defense is either an idiot or lying. The law is purposefully vague so as to force each case to be decided not by precedent but on its own merits. There are no bright lines, just four lines. And those lines are very very blurry. How a judge or jury will see them is up in the air.
And finally, with the level of disagreement found among experts, courts, scholars and others it is highly unlikely that any blogger, including myself, really understand fair use. We may have educated guesses, but ultimately they are just that.